Skip to content
GST Hisab

GST Calculator with Discount

Apply a percentage or fixed discount and a quantity, then GST — the way a correct invoice does it.

Discount, then GST

GST Rate
Special & older rates

3% gold/silver/jewellery · 1.5% & 0.25% specified stones. 12% still applies to bricks, fly ash blocks and roofing tiles; otherwise 12% and 28% are for supplies before 22 Sep 2025 (28% on tobacco until 31 Jan 2026).

GST Type (Supply)

Discount is deducted before GST — valid when it is shown on the invoice at the time of supply (Section 15(3)(a), CGST Act).

Calculation Breakdown

Enter an amount to see the taxable value, CGST, SGST, IGST and total — results update as you type.

Discount before GST, not after

Under Section 15(3)(a) of the CGST Act, a discount given before or at the time of supply and recorded on the invoice is excluded from the taxable value. GST is then charged on the reduced price.

Taxable value = (Price × Qty) − Discount  ·  GST = Taxable value × Rate ÷ 100

Example: 2 pieces at ₹2,000 each, 10% discount, 18% GST. Gross ₹4,000; discount ₹400; taxable value ₹3,600; GST ₹648; final payable ₹4,248.

Discounts after the sale are different

A post-supply discount (year-end volume rebate, later settlement) reduces taxable value only if it was agreed before the supply, is linked to specific invoices, and the recipient reverses the related input tax credit — usually through a credit note (Section 15(3)(b)). Discounts that don’t meet these conditions do not reduce GST. This calculator models the simple on-invoice case only.

Free items and “buy one get one”

Offers like BOGO are generally treated as a single supply at the total price charged, not as free supplies. Treatment varies with facts; confirm with your adviser.

FAQs

Is cash discount allowed before GST?
If the cash discount is known and shown on the invoice at the time of supply, yes. If it is given later for early payment, it reduces GST only when the Section 15(3)(b) conditions are met.
Can the discount be a fixed rupee amount?
Yes — choose ₹ fixed. It is applied to the line total (price × quantity) and capped at that total.

More GST tools